A maximum likelihood procedure for a universal adaptation method based on HMM composition

This paper proposes an adaptation method for universal noise (additive noise and multiplicative distortion) based on the HMM composition (compensation) technique. Although the original HMM composition can be applied only to additive noise, our new method can estimate multiplicative distortion by maximizing the likelihood value. The signal-to-noise ratio is automatically estimated as part of the estimation of multiplicative distortion. Phoneme recognition experiments show that this method improves recognition accuracy for noisy and distorted speech.